“ It is a cockroach! ” I am sure that many of you will think this while looking at the pictures, but don’t get fooled by its appearance! It has nothing to do with those great decomposers and occasional unwanted roommates that you may be sharing your accommodation with. 𝘓𝘪𝘨𝘪𝘢 𝘦𝘹𝘰𝘵𝘪𝘤𝘢 Roux 1828, also known as sea roach, has a wide tropical and subtropical distribution 🌴, frequently found on the wall of harbours and ports with size between 15-20mm. Sea roach is actually more closely related to crabs than cockroaches. Similar to crabs 🦀 , it has a hard shell that provides protection for its soft body. By looking carefully, its head has a pair of distinctively long antennae and its body possesses seven pairs of segmented legs (only 3 pairs in insects). With that many pairs of legs, sea roach can move very fast!
By its name, sea roach, you may guess it lives in marine habitat 🌊 but don’t get fooled again! It lives in rocky intertidal habitats, like rocky beaches, where the area is exposed to the air during low tide while the place is fully covered with water during high tide. As living between land and the sea, 𝘓.𝘦𝘹𝘰𝘵𝘪𝘤𝘢 has a combined terrestrial and aquatic characteristic. Terrestrial animals need moist air to lower evaporation on the surface to avoid water loss while aquatic animals dry out quickly since the body can only resist little water loss. 𝘓.𝘦𝘹𝘰𝘵𝘪𝘤𝘢 has to tolerate dry conditions since water retreats during low tide and such an environment can become very hot quickly ☀️. When exposed to dry conditions, its weight can decrease by 10% within three hours. To replenish the water lost through desiccation, the direct water uptake is needed. Once its antennae locate the water's surface, it will approach the surface with its front legs. Once it finds a suitable place, it will then appose the other two pairs of specialized legs firmly and absorb the water from its legs. What a special taste!
Although 𝘓.𝘦𝘹𝘰𝘵𝘪𝘤𝘢 looks for water, it won't dive into the sea to avoid predation by marine organisms. This little animal is well adapted to the rocky surface, hiding in crevices of rocks. Only when escaping terrestrial hunters or being carried away by wave action, it gets into the sea. With the perfect skills of walking, it can walk through the waves and climb up the rocks, picking up various kinds of wave products like decomposed vegetation, detritus, etc. on the waterside of the intertidal zone. If it gets close to you, no worries, it won’t bite you unless you are already dead 💀!
At the HKBM, come and visit this roach-like animal and thousands more!
Text: Joyce Chan
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